Electrode for lead acid storage battery

ABSTRACT

An electrode for a lead acid battery is provided. The electrode includes a pasting material distributed on the electrode and arranged to provide uniform current density. A lead acid battery having a plurality of electrodes, each electrode having pasting material providing uniform current density across the electrodes is also provided. A method for manufacturing a battery electrode is also provided and includes applying a portion of the electrode with a pasting material providing uniform current density.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application,Ser. No. 61/296,502, filed Jan. 20, 2010, entitled “Electrode for LeadStorage Battery,” and International Application PCT/US2011/021872 theentire contents of which are hereby incorporated by reference in theirentirety herein.

FIELD

The present inventions relate to the field of batteries (e.g. lead-acidbatteries including batteries for vehicle starting, lighting andignition applications; marine batteries; commercial batteries;industrial batteries; batteries for use with hybrid-electric vehicles,microhybrid vehicles, etc.). The present inventions more specificallyrelate to a lead storage battery electrode and a method formanufacturing same, and more particularly, to an electrode for a leadstorage battery including a pasting material or paper with variableresistance.

BACKGROUND

Lead acid batteries are widely known as secondary batteries used in mostvehicles. A typical lead acid battery may include several electrodessubstantially submerged in an electrolyte (e.g., aqueous sulfuric acid).The electrodes include anodes, which may be made of an active materialsuch as lead or a lead alloy, and cathodes, which may be made of anactive material such as lead dioxide or another lead alloy. Theelectrodes chemically interact with the electrolyte to convert chemicalenergy into electrical energy and in some cases convert electricalenergy into chemical energy. The electrodes typically include collectionlugs.

Often, the electrodes are manufactured as pasted grids. Such electrodesmay include a lead or lead alloy grid and a paste that includes redlead, dilute sulfuric acid and/or other additives, such as, for example,expanders. Paste may be provided on the grids and/or pressed intoapertures defined by the grids and may then be dried or allowed to dry.Pasting paper may be provided on the electrodes during or after thepasting process.

Traditional batteries may also include separators provided between theelectrodes. The separators may be made from, for example, wood, rubber,glass fiber, cellulose, sintered PVC/polyethylene, and/or any otherknown or later-developed insulating or non-electrically-conductivematerial.

A common occurrence in lead acid batteries is acid stratification. Acidstratification generally refers to the non-uniform concentration ofelectrolyte fluid within a lead acid battery. The electrolyte in astratified battery concentrates toward the bottom, causing the upperhalf of the cell to be acid poor. Acid stratification may result fromthe battery being kept at a low charge without being fully chargedduring several charge/discharge cycles. For example, a vehicle that isonly driven short distances often does not fully charge its starting,lighting and ignition (SLI) battery between successive starts of thevehicle. As a result, the battery may be maintained at a partial chargefor an extended period of time and acid stratification may result. Acidstratification may reduce the performance of the battery and mayeventually lead to a premature failure of the battery.

Acid stratification may also lead to sulfation in particular regions ofthe electrodes, such as for example on the lower portions of theelectrodes. Sulfation generally refers to the formation of lead sulfateon one or more electrodes of a battery. Sulfation may result incrystallized lead sulfate formations that are difficult to break up orreturn to active material in the electrode and/or the electrolyte andmay result in a loss of active material available to the electrode andthe battery as a whole. Further, acid stratification and/or sulfation ina battery may result in the battery measuring a higher than actual opencircuit voltage. As a result, the battery may appear to be fully chargedwhen it actually may be only partially charged and may have a lower thanexpected cold cranking amps (CCA) value.

It has been found that uneven current density between two or moreelectrodes of a lead acid battery may contribute to acid stratificationand/or sulfation within the lead acid battery.

SUMMARY

Accordingly, an electrode for a lead acid battery is provided. Theelectrode has a pasting material distributed on the electrode andarranged to provide uniform current density.

A lead acid battery is further provided. The lead acid battery includesa plurality of electrodes. Each electrode is provided with a pastingmaterial distributed on the electrode and arranged to provide uniformcurrent density across the electrodes.

A method for manufacturing a battery electrode is also provided. Themethod includes applying a portion of an electrode with a pastingmaterial so as to provide uniform current density.

These and other features and advantages of various embodiments ofsystems and methods according to this invention are described in, or areapparent from, the following detailed description of various exemplaryembodiments of various devices, structures, and/or methods according tothis invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Various examples of embodiments of the systems and methods according tothe present disclosure will be described in detail, with reference tothe following figures, wherein:

FIG. 1 is an isometric view of a vehicle including a battery accordingto one or more examples of embodiments;

FIG. 2 is an isometric cut-away exploded view of a portion of a batteryaccording to one or more examples of embodiments;

FIG. 3 is a front plan cut-away view of a portion of a battery plate orelectrode (e.g. positive battery plate) comprising a stamped grid andactive material according to one or more examples of embodiments;

FIG. 4 is a front plan view of a stamped grid (e.g. positive grid)according to one or more examples of embodiments;

FIG. 5 is an isometric cut-away view of a battery plate or electrode(e.g. negative battery plate) and separator according to one or moreexamples of embodiments;

FIG. 6 is a schematic representation of the relative current densitypassing between two electrodes (e.g., an anode and a cathode) of aconventional battery or pre application of the pasting materialaccording to one or more examples of embodiments;

FIG. 7 is a schematic representation of the relative current flowpassing between two electrodes (e.g., an anode and a cathode) of abattery with a pasting material according to one or more examples ofembodiments;

FIG. 8 is a front plan view of an electrode provided with a pastingmaterial according to one or more examples of embodiments;

FIG. 9 is a perspective view of a method of manufacturing or modifying apasting material shown in FIG. 8 according to one or more examples ofembodiments;

FIG. 10 is a front plan view of an electrode provided with a pastingmaterial according to one or more examples of embodiments;

FIG. 11 is a perspective view showing one or more examples of theapplication of a pasting material to an electrode;

FIG. 12 is a perspective view of a method of providing a pastingmaterial for use in manufacturing, according to one or more examples ofembodiments;

FIG. 13 is a perspective view of a method of providing a pastingmaterial shown in FIG. 14 according to one or more examples ofembodiments;

FIG. 14 is a front plan view of an electrode provided with a pastingmaterial according to one or more examples of embodiments.

It should be understood that the drawings are not necessarily to scale.In certain instances, details that are not necessary to theunderstanding of the invention or render other details difficult toperceive may have been omitted. It should be understood, of course, thatthe invention is not necessarily limited to the particular embodimentsillustrated herein.

DETAILED DESCRIPTION

Referring to FIG. 1, a vehicle 20 is shown that includes a battery 22according to one or more examples of embodiments. FIG. 1 depicts avehicle 20 with an electrical power storage device 22 (e.g., a battery).The size, shape, configuration, and location of an electrical powerstorage device and the type of vehicle may vary according to variousexamples of embodiments. For example, while the vehicle 20 shown is anautomobile, according to various examples of embodiments, the vehiclemay comprise a wide variety of different types of vehicles, including,among others, motorcycles, buses, recreational vehicles, boats, and thelike. The electrical power storage module 22 may supply power forvarious vehicles, including, for example electric powered vehicle,hybrid electric vehicles, and gasoline powered vehicles. According toone or more examples of embodiments, the vehicle 20 uses an internalcombustion engine or a hybrid or other drive for locomotive purposes.

The battery 22 shown in FIG. 1 is configured to provide at least aportion of the power required to start or operate the vehicle 20 and/orvarious vehicle systems (e.g., starting, lighting and ignition systems).Further, it should be understood that the battery 22 may be utilized ina variety of applications not involving a vehicle, and all suchapplications are intended to be within the scope of the presentdisclosure.

The battery 22 shown in FIG. 1 may include any type of secondary battery(e.g., rechargeable battery). According to one or more examples ofembodiments, the battery includes a lead-acid storage battery. Variousembodiments of lead-acid storage batteries may be either sealed (e.g.,non-maintenance) or unsealed (e.g., wet). According to one or moreexamples of embodiments, the lead-acid storage battery is an unsealedlead-acid battery and periodically requires the addition of electrolyteand/or water to maintain a desired volume and/or concentration of eitheror both.

A lead-acid storage battery 22 according to one or more examples ofembodiments is illustrated in FIG. 2. FIG. 2 depicts a cutaway explodedisometric view of an electrical power storage device 22 according to oneor more examples of embodiments. The electrical power storage device 22includes a plurality of electrochemical electrodes or plates 24, 26 andplate sets, generally designated 28 (e.g., lead-acid). Otherconfigurations and electrical power storage devices, such as a battery,may be used in accordance with various other examples of embodiments. Invarious embodiments, the lead-acid storage battery 22 includes severalcell elements which are provided in separate compartments of a containeror housing containing electrolyte. The illustrations provided hereinrelate to automotive applications, wherein groups of 12-16 plates areused in each of six stacks for producing a standard automotive 12-voltbattery. It will be obvious to those skilled in the art after readingthis specification that the size and number of the individual grids, thesize and number of plates in any particular stack, and the number ofstacks used to construct the battery may vary widely depending upon thedesired end use.

In various embodiments, the battery housing 30 includes a box-like baseor container and is made of a moldable resin. A plurality of plateblocks are connected in series according to the capacity of the leadstorage battery and are accommodated in the battery container or housingtogether with the electrolyte, which is most commonly aqueous sulfuricacid.

In various embodiments, the battery 22 includes a compartment 30 havinga front wall, end walls, a rear wall and a bottom wall. In variousembodiments, five cell partitions or dividers are provided between theend walls, resulting in the formation of six compartments, as typicallywould be present in a twelve volt automotive battery. In variousembodiments, a plate block is located in each compartment, each plateblock including one or more positive and negative plates 24, 26, eachhaving at least one lug 60, 68, and optionally a separator material 32placed between each positive and negative plate 24, 26.

A cover 34 is provided for the housing 30, and in various embodiments,the cover includes terminal bushings and fill tubes to allow electrolyteto be added to the cells and to permit servicing. To prevent undesirablespillage of electrolyte from the fill tubes, and to permit exhausting ofgases generated during the electrochemical reaction, a battery may alsoinclude one or more filler hole caps and/or vent cap assemblies.

At least one positive and negative terminal post, generally designated36, may be found on or about the top or front compartments of thebattery. Such terminal posts 36 typically include portions which mayextend through the cover and/or the front of the battery housing,depending upon the battery design. In various embodiments, the terminalposts 36 also extend through a terminal post seal assembly to helpprevent leakage of acid. It will be recognized that a variety ofterminal arrangements are possible, including top, side or cornerconfigurations known in the art.

FIG. 2 also shows an example of conventional cast-on-strap 38 whichincludes a rectangular, elongated body portion of a length sufficient toelectrically couple each lug in a plate set and an upwardly extendingmember having a rounded top. FIG. 2 also illustrates a cast-on-strap 38coupling lugs to a negative terminal 40. As shown in FIG. 2, accordingto various embodiments, the strap includes a body portion coupling therespective lugs in the end compartments and a post formed therewith toprotrude through a cover.

Each cell element or chapter includes at least one positive plate 24, atleast one negative plate 26, and optionally, a separator 32 positionedbetween each positive and negative plate. Separators 32 are generallyprovided between the plates to prevent shorting and undesirable electronflow produced during the reaction occurring in the battery.

Positive and negative electrode plates can be classified into varioustypes according to the method of manufacturing the same. As one example,a paste type electrode is shown in FIGS. 3-5. In various embodiments,the paste type electrode includes a grid substrate 42, 46 and anelectrochemically active material or “paste” 48, 50 provided on thesubstrate. The grid may be formed of a soft alloy containing a trace ofcalcium for enhancing the mechanical strength of the substrate.

Referring to FIGS. 3-5, the positive and negative plates 24, 26 eachcomprise a lead or lead alloy grid 42, 46 that supports anelectrochemically active material 48, 50. The grids provide anelectrical contact between the positive and negative active materials orpaste 48, 50 which serves to conduct current. The grids 48, 50 asindicated also serve as a substrate for helping supportelectrochemically active material (e.g., paste) deposited or otherwiseprovided thereon during manufacture to form battery plates.

As set forth in greater detail below, known arts of lead acid batterygrid making include: (1) batch processes such as book mold gravitycasting; and (2) continuous processes such as strip expansion, stripstamping, continuous casting, and continuous casting followed byrolling. Grids made from these processes tend to have unique featurescharacteristic of the particular process and behave differently in leadacid batteries, especially with respect to the pasting process. Itshould be appreciated that grids formed from any conventional orlater-developed grid manufacturing process may be utilized, and it isnot the intent to limit the invention to the grid design disclosedherein.

In various embodiments, at least some of the grids are stamped grids.FIG. 3 illustrates one or more examples of embodiments of a stamped grid42 (e.g. a grid for a positive plate) with active material or paste 48provided thereon. FIG. 4 illustrates the stamped grid 42 shown in FIG.3, but without active material. In various embodiments, the stamped grid42 includes a frame that includes a top frame element 52, first andsecond side frame elements 54, 56, and a bottom frame element 58. Invarious embodiments, the stamped grid 42 includes a series of grid wires44 that define open areas that help hold the active material or paste 48that helps provides current generation. In various embodiments, acurrent collection lug 60 is integral with the top frame element 52.While FIGS. 3-4 depict the lug 60 as offset from the center of the topframe element 52, the lug may alternatively be centered or positionedcloser to either the first or second side frame elements 54, 56. The topframe element 52 may include an enlarged conductive section at least aportion of which is directly beneath the lug 60 to optimize currentconduction to the lug.

The bottom frame element 58 may be formed with one or more downwardlyextending feet (not shown) for spacing the remainder of the grid 42 awayfrom the bottom of the battery container. In various embodiments, atleast some of the wires 44 increase in cross-sectional area along theirlength from bottom to top or have a tapered shape so as to optimize thecurrent carrying capacity of the wires to help carry away increasingcurrent being generated from the bottom to the top. The width andspacing of the wires 44 between side elements 54, 56 may bepredetermined so that there are substantially equal potential pointsacross the width of the grid 42. To assist in supporting theelectrochemical paste 48 and/or permit the formation of paste pellets,in various embodiments, the stamped grid 42 also includes horizontalwires 62 which are equally spaced apart and are parallel to the topand/or bottom frame elements 52, 58. As shown in FIG. 3-4, however, atleast some of the horizontal wires 62 may not be equally spread apart orparallel to the top and/or bottom frame elements.

Various stamped grid designs may be utilized. See, e.g., U.S. Pat. Nos.5,582,936; 5,989,749; 6,203,948; 6,274,274; 6,921,611; and 6,993,641;and U.S. patent application Ser. Nos. 10/996,168; 11,086,525;10,819,489; and 60/904,404, each of which are incorporated herein byreference in their entireties. It should be noted that an infinitenumber of grid designs may be utilized and therefore, it is not theintent of the following description to limit the invention to the griddesign shown in FIGS. 3-5, which are presented for the purposes ofillustration.

One or more examples of embodiments of an expanded metal grid 46 (e.g. agrid for the negative plate) are illustrated in FIG. 5. In variousembodiments, the expanded metal grid 46 has a pattern (e.g., a diamondpattern such as that shown in FIG. 5), which is well known in the art,with a bottom frame element 64, and a top frame element 66 that isintegral with a lug 68.

Referring to FIGS. 3-5, the cross-section of the grid wires 44 may varydepending upon the grid making process. To help improve adhesion of thebattery paste, however, in various embodiments, the grid wires may bemechanically reshaped or refinished. It should be appreciated that anynumber of grid wire shapes may be utilized as long as the shape providessuitable paste adhesion characteristics. For example, the cross sectionof wires may be of any cross-section design including substantially ovalshaped, substantially rectangular, substantially diamond shape,substantially rhomboid shape, substantially hexagon shape, and/orsubstantially octagon shape. In the battery grid, each grid wire sectionmay have a different cross-sectional configuration, or each grid wiresection may have the same or a similar cross-sectional configuration.However, it is preferred that each grid wire section have the samecross-sectional configuration. Depending on the needs, a grid can bedeformed at the vertical wire elements only, the horizontal wireelements only, or at both the vertical and horizontal wire elements.

The active material or paste 48, 50 is typically a lead-based material(e.g. PbO, PbO₂, Pb or PbSO₄ at different charge/discharge stages of thebattery) that is pasted, deposited or otherwise provided onto the grids42, 46. The paste composition may be determined by power requirements,cost and battery environment, as it is known in the art. In variousembodiments, the active material of a lead-acid battery is prepared bymixing lead oxide, sulfuric acid and water. The lead oxide reacts withthe sulfuric acid to form mono-, tri- and/or tetrabasic lead sulfate(s).Dry additives, such as fiber and expander, may also be added to theactive material. For example, in various embodiments, expanders such asfinely-divided carbons (e.g. lampblack or carbon black), barium sulfateand various lignins may be included in the active material. In variousembodiments, the mixture is then dried and water is re-added to form apaste of the desired consistency.

The active material 48 provided on the positive grid 42 (e.g. leaddioxide [PbO₂]), is typically in micro-particle form, so that theelectrolyte is allowed to diffuse and permeate through the lead dioxidemicroparticles on the positive electrode plate 24. The spongy lead, theactive material 50 of the negative electrode plate 26, is typicallyporous and reactive, so that the electrolyte is allowed to diffuse andpermeate through the sponge lead on the negative electrode plate.

As shown in FIG. 2, in various embodiments, active materials 48, 50 aredeposited in paste form on the positive and negative grid 42, 46 tocreate the positive plate 24 and negative plate 26, respectively. Toprevent the separation of active materials 48, 50 from the plates, andto improve handling of the active materials in the manufacture ofelectrodes 24, 26, a pasting material or paper 70 is provided to theactive material after deposition on the grids. The pasting paper 70 maybe provided in or on an electrode 24, 26 of a lead acid battery. Inparticular, the pasting paper or material 70 may be adhered or otherwiseprovided on at least one of the surfaces of the active material 48, 50as, among other things, a support to the active material afterdeposition on the grids 42, 46. Each electrode 24, 26 may be providedwith a pasting material 70 and the electrodes may be placed in closeproximity to each other within the battery 22. In one or more examplesof embodiments described herein, the distance between adjacentelectrodes 24, 26 may range from approximately 1.0 mm to approximately4.0 mm such that the pasting materials of the adjacent electrodes maycontact each other or at least be in close proximity to each other.While specific ranges are provided, it is contemplated that the pastingmaterials or electrodes may otherwise be placed in relative closeproximity suitable to accomplish the purposes of the present invention.

In one or more examples of embodiments, the pasting material 70described herein is used to provide a more uniform current densityacross or between the electrodes 24, 26. FIG. 6 shows the currentdensity between two plates or electrodes 24, 26 of a typical lead acidbattery 22. As shown in FIG. 6, the current (A) may be more dense towardthe top 72 of the electrodes, such as for example closer to a collectionlug 60, 68 of each electrode 24, 26, and the current (B) may be lessdense toward the bottom 74 of the electrodes, such as for examplefurther from the collection lug of each electrode. The non-uniformnature of the current density in a typical lead acid battery can resultfrom a non-uniform internal resistance within the battery. There may beless resistance between two electrodes 24, 26 closer to the collectionlugs 60, 68 of those electrodes than farther from the lugs. As a result,more current may flow (A) in areas of decreased resistance (e.g.,closest to the terminals 36). The decreased current flow (B) towards thebottom 74 of the electrodes (e.g., areas of increased resistance), atleast in relation to the areas of decreased resistance shown in FIG. 6,can contribute to acid stratification and/or an increase in theproduction of lead sulfates. The resulting acid stratification and/orproduction of lead sulfates may further reduce the current flow in theseregions due to, for example, a reduction in the available activematerial in the electrode, and may eventually lead to a prematurefailure of the battery.

By comparison, FIG. 7 shows a more uniform current density across theelectrodes that may result from the use of a pasting material 70according to one or more examples of embodiments described herein. Invarious embodiments, the current density (A) closest to the collectionlugs 60, 68 of the electrodes 24, 26 may be decreased by increasing theresistance of the electrode in this location, at least relative to theresistance further from the collection lugs of the electrode, which mayalso increase current density (B) further from the collection lugs ofthe electrode. In various embodiments, the resistance of the electrodes24, 26 in regions farther from the collection lugs 60, 68 may bereduced, at least relative to the resistance closer to the collectionlugs, to increase the current density in such regions. It should beappreciated that increasing a resistance in a first area may have thesame relative effect as decreasing a resistance in a second area.

The pasting material 70 may be formed or made of any suitable materialfor the purposes provided herein. According to the present invention,the pasting material 70 may be formed of one or more papers, wovenfabrics, and/or non-woven fabrics such as but not limited to non-wovenfabrics formed of polyesters, polypropylenes, or viscose rayon. Forexample, the pasting material may be paper or porous nonwoven fabrichaving micron-sized pores. As another example, the pasting material maybe a nonwoven fabric synthesized from thermoplastic resin byspun-bonding or thermal-bonding.

The pasting material 70 may be provided with varying density and/orthickness to provide for varying resistance. To this end, the pastingmaterial may vary continually (e.g., linearly), and/or incrementally(e.g., in a stepped manner) between two positions. For example, thedensity and/or thickness of the pasting material 70 may graduallyincrease in a linear manner from or between a top edge or portion 72 ofthe electrode 24, 26 towards a bottom edge or portion 74 of theelectrode. The density and/or thickness of the pasting material 70 mayalso vary in a number of incremental steps from or between the top edgeof the electrode toward the bottom edge of the electrode. It should alsobe appreciated that the density and/or thickness of the pasting paper ormaterial may vary in one or more dimensions. For example, rather thanthe density gradually varying from the top edge toward the bottom edge,the density may vary in a more radial, three-dimensional fashion awayfrom a region or single point such as but not limited to the lug of theelectrode. Preferably, the density of the pasting material is providedin a form or arrangement that maximizes the uniform current distributionor uniform current density between adjacent electrodes. In one or morealternative examples of the pasting material, current density can alsobe varied to increase resistance near the top of the plate and todistribute or force more current density lower in the electrode.

In one or more examples of the pasting material 70 usable in themanufacture of a lead acid battery, a pasting material 76 may define orinclude apertures or pores 78 that are mechanically formed, naturallyoccurring, pre-formed, or otherwise provided in the pasting paper ormaterial. The apertures or pores 78 defined in the pasting paper ormaterial 76 may vary in size and/or density to follow the current flowof a grid or electrode, or more specifically to correspond with thecurrent distribution profile of the electrode. For example, the poresmay be provided such that the pasting paper 76 may be least porousclosest to a collection lug 60, 68 of the electrode 24, 26 and may bemost porous furthest from the collection lug of the electrode. Morespecifically, the material 76 may be least porous where the current istraditionally or typically the most dense and may be most porous wherethe current is traditionally or typically the least dense betweenelectrodes, or otherwise causing more current at the furthest point fromthe collection lug. FIG. 8 shows a battery electrode 24 provided withone or more examples of embodiments of a pasting material 76. Thepasting material defines or is formed of or includes one or more pores,apertures, or openings 78. In the illustrated embodiment, a plurality ofpores 78 are provided spaced across a pasting material or sheet orpaper. The pores 78 may vary in size and/or frequency to help reduce therelative density of the pasting paper further from the lugs. Larger or agreater volume of pores generally may provide a greater or easiercurrent flow. While a specific battery electrode and arrangement ofpasting material is illustrated in the Figures and described herein,alternative forms of electrode and arrangements of pasting material andpores may be acceptable for the purposes provided. It should also beappreciated that, although the pores 78 in the pasting paper are shownin the Figures as circular and macroscopic pores 78 (e.g., visible to anunaided eye), the pores 78 may be any size and shape. According tovarious examples of embodiments, the pores 78 are microscopic and notvisible to an unaided eye. Further, varying size and shape pores may beprovided in any suitable pattern to accomplish the intended purposes.

The pasting material or paper 76 of FIG. 8 may be formed in or by anysuitable manner. FIG. 9 shows one or more examples of method ofproviding a pasting paper or material of FIG. 8 with varying density orpores 78. In various embodiments, the pasting material 76 may beperforated by any known or later-developed method. The pasting material76 may be perforated according to any desired pattern to create avarying density by size and/or frequency of the perforations or pores 78in the pasting paper or material. As outlined above, the perforations 78may be macroscopic, microscopic, round and/or any other shape and/orsize. In general, the size and/or frequency of the pores 78 provided inthe pasting paper 76 may increase in regions that will be providedaround an electrode 24 farthest from a collection lug 60 of theelectrode and may decrease in regions that will be provided closest tothe collection lug of the electrode, or at least vary in relation torespective spaced apart regions.

The pasting paper or material 76 may be provided on a roll or other feeddevice 80. The pasting paper 76 may be provided on continuous orseparate sheets. The pasting material 76 may be passed over a punch ordie 82 or other device or a plurality of such devices having one or moreshaped protrusions 84 of one or more shapes and one or more sizes. Thedie 82 may further be movable or rotatable to position the respectiveprotrusions 84 for suitable placement of pores 78 on the pastingmaterial 76. While large protrusions 84 are shown in FIG. 9 for ease ofillustration, the protrusions may be of any size to accommodatemanufacturing or desired resistance properties. Before being applied tothe plates 24, 26, the pasting material is or may be perforated asdescribed above via an adapted manufacturing device.

In one or more examples of the pasting material described herein, thepasting material 70 is usable in the manufacture of a lead acid batteryand may include a varying density, thickness and/or resistance. Thepasting material 70 may be wrapped around an electrode or otherwiseapplied to a surface or portion of a surface of an electrode in a leadacid battery such that the pasting paper may be more dense, thickerand/or may have a greater resistance in a particular region of theelectrode, such as closer to a collection lug of the electrode, and maybe less dense, thinner and/or may have a lower resistance in a secondregion, such as further from the collection lug.

FIG. 10 shows one or more examples of a pasting paper or material 70 onan electrode 24 according to this invention. While a specific electrodeand pasting material arrangement are shown in the Figures, alternativepasting material arrangements and electrodes are acceptable for thepurposes provided. In this embodiment, the pasting material 86 may bechemically or physically treated or altered such that the material has avarying density and/or varying inherent resistance. As one non-limitingexample, a chemical may be added to any known or later-developed pastingmaterial 86 to increase or decrease the density and/or inherentresistance of the pasting material in desired regions. The pastingmaterial 86 may also be manufactured or physically altered to have avarying density or varying inherent resistance due to a variation in aphysical characteristic. For example, the paper 86 may be manufacturedto have a non-uniform density and/or thickness. In general, thethickness, density and or resistance of the pasting material mayincrease or be higher in regions closest to a lug 60 of an electrode andmay decrease in regions furthest from the lug of the electrode, or atleast vary in relation to respective spaced apart regions.

FIGS. 11-12 show one or more examples of a pasting paper 86 of FIG. 10and the application thereof on an electrode 24 for use in amanufacturing process. The pasting paper or material 86 illustrated inFIGS. 11-12 shows a paper or material 86 of FIG. 10 in sheet form (FIG.11) and in a continuous sheet on a roll (FIG. 12) which may be segmentedor otherwise cut to fit for use with the plates of the presentinvention. However, any of the pasting materials described herein may besubstituted in place of the pasting material illustrated in FIGS. 11-12without departing from the overall invention. In addition, the pastingmaterial may be provided in alternative forms or otherwise formed or fedin known or future developed methods without departing from the overallpurposes provided herein.

In one or more alternative examples of the pasting paper 70, a batteryelectrode 24 may be provided with two or more layers of pastingmaterial. While a specific electrode and pasting material arrangementare shown in the Figures, alternative pasting material arrangements andelectrodes are acceptable for the purposes provided. In one or moreexamples, a first portion 88 of the electrode 24 may be wrapped with orapplied with a first layer of pasting material 90 and a second portion92 of the electrode may be wrapped with or applied with the first layerof pasting material 90 and a second layer of pasting material 94. Thefirst portion 88 may be closer to a particular region, such as acollection lug 60, of the electrode in comparison to the second portion92.

FIGS. 13 and 14 depict a method of providing an electrode 24 with apasting material or paper 70 having a varying resistance according toone or more alternative examples of embodiments. In particular, thepasting material may be layered to build density in different regions ofthe plate or electrode, with the least layered portion (e.g., a singlelayer) being the least dense and having the greatest current. As shownin FIG. 13, three rolls of pasting material 96, 98, 100 of differentsizes and/or types of pasting material are provided. As shown in FIG.14, the rolls of pasting material 96, 98, 100 are provided or secured tothe plate in overlapping layers 90, 94, 102. In one or more examples,the plate 24 is pre-cut before application of the layers but cutting theplate after application of the layers would not depart from the purposesprovided herein. In various embodiments, pasting material from the firstroll 96 is provided substantially on a face or surface of the electrode24 to provide a first layer 90; pasting material from the second roll 98is provided in a second layer 94 over a face or surface of the electrode24 and material from the first roll 96, and in the illustrated example,substantially over the top two thirds of the face and material from thefirst roll; and pasting material from the third roll 100 is providedover the pasting material from the first and second rolls 96, 98, aswell as over the electrode 24, and in the illustrated examplesubstantially over the top third or third portion 106 of the electrode.As such, in the illustrated example approximately the top third of theelectrode may have three layers of pasting paper or material (i.e., eachof the three rolls 96, 98, 100 is applied to this area), approximatelythe middle third may have two layers of pasting paper or material (i.e.,the first roll and second roll 96, 98 are applied to this area) andapproximately the bottom third of the electrode may have one layer ofpasting paper or material (i.e., only the first roll 96 is applied tothis area). While the illustrated example shows a substantiallysegmented arrangement in thirds (⅓ s), it is understood that therespective areas may vary so as to increase or decrease each respectivearea. The areas that have more layers of paper or material (e.g.,towards the collection lug or top of the electrode) may have anincreased density of pasting material and an increased resistance, atleast relative to other portions or regions of the electrode.

It should be appreciated that any number of rolls of pasting materialcan be used to apply any number of layers of pasting material to theelectrode 24, 26. For example, two rolls, four rolls or more than fourrolls could be used to apply different amounts of pasting material todifferent parts of the electrode. It should also be appreciated that,rather than overlapping the layers, separate types of pasting materialthat have different thicknesses, densities and/or inherent resistancesmay be provided adjacent to each other. These varying types of materialsmay also be overlapped. It should also be appreciated that the materialneed not be provided from rolls. Any material source(s) and/ormanufacturing methods may be utilized. To this end, a method formanufacturing a battery electrode 24, 26 is provided. The method mayinclude wrapping or applying at least a first portion 88 of theelectrode with a first pasting material 90 and wrapping or applying atleast a second portion 92 of the electrode with a second pastingmaterial 94. The first portion 88 may be closer to a collection lug 60of the electrode than the second portion 90, or at least may bepositioned in this relation in respective spaced apart regions; and/orthe first pasting material may have a higher resistance, thicknessand/or density than the second pasting material.

It should also be appreciated that the above-outlined examples ofembodiments may be used individually or in combination with each otheror other embodiments. For example, multiple rolls of pasting materialmay be provided with pores 78 of different sizes and/or density andprovided to separate regions of an electrode. Likewise, in addition tobeing provided with pores 78 of varying size and/or density, a pastingmaterial may be treated chemically or otherwise physically altered tocreate pasting material with varying resistance or density.

The pasting material 70 may also help eliminate or reduce the need forseparators 32 in the battery 22. As outlined herein, a lead acid batterymay optionally include separators 32 between any two adjacent electrodes24, 26 to help prevent unintentional electrical flow (e.g., shorts)between the electrodes. A pasting material 70 having a thickness greatenough to provide suitable clearance between electrodes while at thesame time allowing electrolyte or acid migration may be provided. Invarious embodiments, the pasting material 70 according to this inventionis of substantial thickness, density, and/or has other characteristics,at least in one or more regions, which may substantially or partiallyinsulate adjacent electrodes from each other. To this end, pastingmaterial or paper 70 may be usable in the manufacture of or otherwiseprovided in a lead acid battery 22 without the use of a separator. Thepasting material 70 in this example is of suitable thickness to beinsulative and/or non-electrically-conductive. In one or more examples,the pasting material may be formed of a thick poly-material. In one ormore examples, the pasting material 70 may range from approximately 0.3mm to approximately 2.0 mm in thickness with or without ribs, and morepreferably from approximately 0.5 mm to approximately 2.0 mm, orapproximately 0.5 mm to approximately 1.0 mm in thickness with orwithout ribs. While specific ranges are provided, it is contemplatedthat the pasting materials may otherwise be provided with relativedensity or thickness suitable to accomplish the purposes of the presentinvention. The pasting material or paper 70 may be applied to a singleside of the electrode or both sides of the electrode as it is pasted. Itshould be appreciated that the pasting material 70 may be ribbed orotherwise varying in thickness.

The pasting material 70 may also be permeable to an electrolyte oracidic electrolyte of the battery 22. In addition, in various examplesof embodiments, the pasting material 70 that is usable in connectionwith or to replace a separator of the battery may assist in or otherwisesupport the weight of the electrodes 24, 26 thereby reducing the needfor the electrodes to support their own weight and may allow forelectrodes to be made of different materials (e.g., the electrodes mayinclude more pure lead content) or may allow for thinner electrodes orgrids.

As indicated, in various examples of embodiments the pasting material 70is utilized to replace a separator of the battery. In various ones ofthese examples of embodiments, the use of the pasting material and/orthe absence of the separator also advantageously makes the battery morerecyclable, biodegradable, “green” and/or otherwise more environmentallyfriendly. In various examples of embodiments, the utilization of thepasting material to replace the separator also results in electrodesthat dry and/or cure more quickly and/or in a more uniform manner. Invarious examples of embodiments, the electrodes, which include a pastingmaterial that can be utilized to replace a separator of the battery, canalso be stacked during a curing process and help provide an increase inthe amount of air flow around the electrodes during a chemset process.

While not required in one or more examples of embodiments, in variousalternative embodiments one or more battery separators 32 are used toconductively separate the positive and negative electrodes 24, 26. Theseparator material is typically microporous to allow the through passageof ions from the positive and negative electrodes. Separators 32 forautomotive batteries are typically made in continuous lengths androlled, subsequently folded for example as shown in FIG. 5, and sealedalong one or more of their edges to form pouches that receive a batteryplate (e.g. a negative plate as shown in FIG. 5 or a positive plate asshown in FIG. 2).

In various embodiments, separator material 32 generally has asubstantially uniform thickness and a substantially uniform poredistribution. The pore distribution helps ensure an overall uniformcurrent density across the electrodes during operation, thereby helpingachieving a uniform charging and discharging of the electrodes andmaximum battery efficiency. A separator 32 generally incorporates one ormore ribs 104 (e.g. as shown in FIG. 5) to help stiffen the separator.

The separator material 32 may be constructed of a variety of materials(e.g. polyolefin, rubber, phenol-formaldehyde resorcinol, glass mat,microporous PVC, and sintered PVC). In various embodiments, theseparator is comprised of a microporous sheet comprised of highmolecular weight polyolefin. Examples of polyolefins that may be usedinclude polyethylene, polypropylene, polybutene, ethylene-propylenecopolymers, ethylene-butene copolymers, propylene-butene copolymers andethylene-propylene-butene copolymers.

In various embodiments, the separator 32 is also constructed of an inertfiller material. The filler can be soluble or insoluble in water.However, the filler may provide the primary means by which anyplasticizer is absorbed and held in the composition and should not besoluble in the plasticizer. The preferred filler is dry, finely dividedsilica. However, other fillers (e.g. carbon black, coal dust, graphite,metal oxides and hydroxides, metal carbonates, minerals, zeolites,precipitated metal silicates, alumina silica gels, wood flour, woodfibers and bark products, glass particles, salts such as barium sulfate,inorganic salts, acetates, sulfates, phosphates, nitrates, carbonatesand/or combinations thereof) may be utilized. It should also beunderstood that any known or later-developed wetting agents (e.g. sodiumalkyl benzene sulfonate, sodium lauryl sulfate, dioctyl sodiumsulfosuccinate, and isoctyl phenyl polyethoxy ethanol) may be utilizedto enhance the wetability of the filler.

In various embodiments, a separator 32 also includes at least oneplasticizer. The plasticizer may be soluble or insoluble in water.Examples of plasticizers that may be used include organic esters, epoxycompounds, phosphate esters, hydrocarbon materials, and low molecularweight polymers.

In various embodiments, the separator 32 is comprised of a stabilizer oran antioxidant. In various embodiments, conventional stabilizers orantioxidants such as 4,4 thiobis(6-tert-butyl-m-cresol) (“Santonox”),and, 2,6-di-tert-butyl-4-methylphenol (“Ionol”) may be utilized.

When the separator 32 is provided with one or more ribs 104, the ribsmay be formed from a number of known or later-developed polymericcompositions (e.g. the same composition as the separator, otherpolyolefins, polyvinyl chloride, and/or filled or foamed compositionsthereof). The ribs 104 may be provided in any number of ways. Forexample, the ribs may be formed by extrusion (either unitarily with thesheet or separately). The ribs 104 may also be formed by grooving orembossing. When ribs are molded separately, they may be bonded orotherwise coupled to the sheet or base web by any number of methodsknown in the art including heat sealing or by an adhesive.

While a particular rib configuration is shown in FIG. 5, one skilled inthe art will appreciate that any variety of rib configuration may beutilized depending at least in part on the grid design, plate designand/or battery.

The thickness of a separator 32, and to this end the thickness of apasting material 70 used without a separator, will or may vary dependingupon the type of battery 22 in which it is used. In general, thethickness of the base web can range from 1 to 50 mm. For lead-acidbatteries, the preferred thickness range is typically 10 to 40 mm. Theheight of each rib 104 may vary over a wide range depending upon platespacing requirements. Generally, ribs from 5 to 200 mm in height fromthe base are provided, with the preferred range being 10 to 100 mm.

Various chemistries in which the electrochemical potential betweenvarious materials is used to generate electricity have been studied andcommercially implemented. See, in general: Besenhard, J. O., Ed.,Handbook of Battery Materials, Wiley-VCH Verlag GmbH, Weinheim, Germany,1999; and Linden, D., Ed., Handbook of Batteries, Second Edition, McGrawHill Inc., New York, N.Y., 199, both of which are incorporated herein byreference.

A plate 24, 26 for a lead-acid battery is conventionally made byapplying active material or paste to a conductive support such as a leadalloy grid. Plates can be classified according to the method ofmanufacturing the same. For example, one process for producing batteryplates includes an initial step of melting hot lead in a furnace,followed by a step of feeding molten lead alloy to a strip caster. Inthe strip expansion process, a cast or wrought lead strip is typicallypierced, stretched above and below the strip plane, and then pulled orexpanded to form a grid 46 with a diamond pattern. In variousembodiments, the strip is coiled on a winder, and coils of lead alloystrip are stored for later use. In various embodiments, the strip mayalso be rolled. To form a battery grid, in various embodiments, thestrip is fed through an expander that cuts, slits, and stretches a stripof coil to form the grids.

The grids may be produced using other known or later-developedprocesses. For example, as discussed above, the substrate may be formedby a casting process (e.g. by pouring a melted alloy into a mold), astamping process, or by continuous rolling. During the manufacture ofthe grids or the plates, the grid wires may be refinished or reshaped(e.g. to improve adhesion of the paste).

The active material or paste 48, 50 as described herein is then appliedto or otherwise provided (e.g. pasted by a conventional paster) on theexpanded strip or wire grid 42, 46. In various embodiments, one or morepasting materials or pasting papers 70 are provided on one or bothsurfaces of the active material 48, 50. In various embodiments, thepasting materials or paper 70 may be provided in a continuous process.

In various embodiments, the grids 42, 46, active material 48, 50 andpasting material or paper 70 as described herein are fed to a dividerwhere the strip is cut into plates 24, 26. Plates cut from the strip maybe flattened or otherwise modified to help smooth out any uneven regionsof paste. In various embodiments, the plates pass (e.g. on a conveyor)through an oven for flash-drying, and may then be stacked for later use.Conventionally, flash-drying may be performed using an open gas flame oran oven, e.g., as a 10-15 second drying of the plates in a conventionalblast drying oven at about 260 deg C. (about 500 deg F.). After drying,the battery plates undergo a chemical treatment, well known to thoseskilled in the art. The pasted plates are next typically cured for manyhours under elevated temperature and humidity to help oxidize any freelead and otherwise adjust the crystal structure of the plate.

Conventional polyolefin battery separators 32, if used, are typicallyproduced by a process that comprises blending a composition of highmolecular weight polyolefin, an inert filler material, and/or aplasticizer, forming the composition into sheet form, and subsequentlyextracting a portion of the inert filler and/or plasticizer from thesheet using a solvent.

After curing, the plates 24, 26 are assembled into batteries 22.Groupings of individual battery plates may be assembled, enveloped,interleaved or otherwise separated with separator material, and providedtogether to form plate sets 28. For example, in one common batterydesign, every other plate (e.g. each negative plate) in the battery setis inserted into a battery separator in the form of an envelope. Theenvelope acts as a separator between the plate in the envelope and theadjoining plates in the battery set. The plate sets are assembled in acontainer to help form a battery.

During assembly, the positive lugs 60 of the battery plates 24 arecoupled together and the negative lugs 68 of the battery plates 26 arecoupled together. This is typically accomplished using cast-on straps 38formed by taking assembled battery stacks, inverting them, and dippingthe lugs into molten lead provided in a mold. To permit current tofollow throughout the battery, cast-on straps 38 of stacks are joined orcoupled. Moreover, terminal electrodes 36 are provided which extendthrough the cover or casing to permit electrical contact with avehicle's electrical system or other system requiring or intended to usebattery power.

In various embodiments, the battery housing 30, including the cover 34,is provided containing the battery cells. In various embodiments, thebattery housing 30 is submerged in acidic electrolyte fluid in order tofill the battery housing with electrolyte fluid through the fill tubeholes in the battery cover 34. After filling the battery housing 30 withelectrolyte fluid, the battery 22 is removed from the electrolyte fluid.Any residual electrolyte fluid coating, dust, and other debris may bewashed away to prepare the battery for shipment. Before washing thebattery housing external surfaces, the fill tube holes may be plugged toprevent washing fluid from entering the battery housing.

Following the initial wash, the batteries 22 are electrochemicallyformed by passage of current to convert the lead sulfate or basic leadsulfate(s) to lead dioxide (positive plates) or lead (negative plates).This is referred to as the “formation” process.

The electrode, lead acid battery and method of forming the electrodeand/or battery provide various advantages over existing battery designs.For example, an electrode having the pasting material described hereinprovides for even current density between electrodes. As a result, theelectrode and pasting material reduce, or at the least, do notcontribute to acid stratification and/or sulfation within the lead acidbattery. In addition, a pasting material as provided herein that isusable in connection with, or to replace a separator of the battery mayassist in or otherwise support the weight of the electrodes, therebyreducing the need for the electrodes to support their own weight and mayallow for electrodes to be made of different materials (e.g., theelectrodes may include more pure lead content) or may allow for thinnerelectrodes or grids. Moreover, as indicated herein in various examplesof embodiments, the use of the pasting material and/or the absence ofthe separator also advantageously makes the battery more recyclable,biodegradable, “green” and/or otherwise more environmentally friendly.The utilization of the pasting material to replace the separator alsoresults in electrodes that dry and/or cure more quickly and/or in a moreuniform manner. In addition, the electrodes which include a pastingmaterial that can be utilized to replace a separator of the battery canalso be stacked during a curing process and help provide an increase inthe amount of air flow around the electrodes during a chemset process.These and other objects and advantages will be apparent from theforegoing description and appended claims.

As utilized herein, the terms “approximately,” “about,” “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims.

It should be noted that references to relative positions (e.g., “top”and “bottom”) in this description are merely used to identify variouselements as are oriented in the Figures. It should be recognized thatthe orientation of particular components may vary greatly depending onthe application in which they are used.

For the purpose of this disclosure, the term “coupled” means the joiningof two members directly or indirectly to one another. Such joining maybe stationary in nature or moveable in nature. Such joining may beachieved with the two members or the two members and any additionalintermediate members being integrally formed as a single unitary bodywith one another or with the two members or the two members and anyadditional intermediate members being attached to one another. Suchjoining may be permanent in nature or may be removable or releasable innature.

It is also important to note that the construction and arrangement ofthe battery or electrodes as shown in the various examples ofembodiments is illustrative only. Although only a few embodiments havebeen described in detail in this disclosure, those skilled in the artwho review this disclosure will readily appreciate that manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter recited. For example,elements shown as integrally formed may be constructed of multiple partsor elements show as multiple parts may be integrally formed, theoperation of the interfaces may be reversed or otherwise varied, thelength or width of the structures and/or members or connector or otherelements of the system may be varied, the nature or number of adjustmentpositions provided between the elements may be varied (e.g. byvariations in the number of engagement slots or size of the engagementslots or type of engagement). The order or sequence of any process ormethod steps may be varied or re-sequenced according to alternativeembodiments. Other substitutions, modifications, changes and omissionsmay be made in the design, operating conditions and arrangement of thevarious examples of embodiments without departing from the spirit orscope of the present inventions.

While this invention has been described in conjunction with the examplesof embodiments outlined above, various alternatives, modifications,variations, improvements and/or substantial equivalents, whether knownor that are or may be presently foreseen, may become apparent to thosehaving at least ordinary skill in the art. Accordingly, the examples ofembodiments of the invention, as set forth above, are intended to beillustrative, not limiting. Various changes may be made withoutdeparting from the spirit or scope of the invention. Therefore, theinvention is intended to embrace all known or earlier developedalternatives, modifications, variations, improvements and/or substantialequivalents.

What is claimed is:
 1. An electrode for a lead acid battery comprising:a surface; a pasting material provided on the surface; wherein thepasting material has a physical property which varies across the surfaceof the electrode that provides uniform current density across theelectrode.
 2. The electrode of claim 1, wherein the pasting material hascontinual varying resistance across the surface of the electrode.
 3. Theelectrode of claim 2, wherein the pasting material has a greaterresistance closer to a collection lug of the electrode than a resistancefurther from the collection lug as measured across the surface of theelectrode.
 4. The electrode of claim 1, wherein the pasting material hasvarying physical density.
 5. The electrode of claim 4, wherein thepasting material is chemically treated to provide the varying physicaldensity.
 6. The electrode of claim 1, wherein the pasting material is ofvarying thickness.
 7. The electrode of claim 6, wherein the pastingmaterial has a thickness ranging from 0.5 mm to 2.0 mm.
 8. The electrodeof claim 1, wherein the pasting material is permeable to an electrolyteof the lead acid battery.
 9. The electrode of claim 1 wherein thepasting material is non-electrically-conductive.
 10. The electrode ofclaim 1 wherein the pasting material is insulative.
 11. The electrode ofclaim 1, wherein the pasting material is wrapped around the electrode.12. The electrode of claim 1, wherein the pasting material has aplurality of pores.
 13. The electrode of claim 12, wherein the poresvary in size.
 14. The electrode of claim 13, wherein the pastingmaterial is least porous closest to a collection lug of the electrode.15. The electrode of claim 1, wherein a first portion of the electrodehas a first layer of pasting material and a second portion of theelectrode has the first layer of pasting material and a second layer ofpasting material.
 16. The electrode of claim 15, wherein the firstportion of the electrode is closer to a collection lug of the electrodethan the second portion of the electrode.
 17. The electrode of claim 1,wherein the pasting material has incremental varying resistance.
 18. Theelectrode of claim 1, wherein the pasting material comprises nonwovenfabric.
 19. An electrode for a lead acid battery comprising; a surface;a pasting material provided on the surface; wherein the pasting materialhas a variable thickness as measured across the surface of the electrodethat provides uniform current density across the electrode.
 20. Anelectrode for a lead acid battery comprising: a surface; a pastingmaterial provided on the surface; wherein the pasting material has avariable pore distribution as distributed across the surface of theelectrode that provides uniform current density across the electrode.21. The electrode of claim 1, wherein the pasting material is comprisedof multiple layers of pasting material.
 22. A lead-acid battery havingthe electrode of claim
 1. 23. A lead-acid battery having the electrodeof claim
 19. 24. A lead-acid battery having the electrode of claim 20.25. The electrode of claim 15 wherein the first portion of the electrodedoes not include the second layer of pasting material.
 26. The electrodeof claim 1 wherein the pasting material provided on the surface of theelectrode comprises an interface between the pasting material andelectrode, and the physical property varies as measured across theinterface between the pasting material and surface of the electrode. 27.The electrode of claim 19 wherein the pasting material provided on thesurface of the electrode comprises an interface between the pastingmaterial and electrode, and the variable thickness varies across theinterface between the pasting material and surface of the electrode. 28.The electrode of claim 20 wherein the pasting material provided on thesurface of the electrode comprises an interface between the pastingmaterial and electrode, and the variable pore distribution varies acrossthe interface between the pasting material and surface of the electrode.